Field of the Invention
The invention concerns a system for a motor vehicle for heating and/or cooling a battery and a motor vehicle passenger compartment and a method therefor.
Description of the Background Art
In hybrid vehicles with an internal combustion engine and an electric motor, and also in electric vehicles that are driven by an electric motor alone, an electric heater is generally necessary for heating the air in the vehicle passenger compartment. In hybrid vehicles with an internal combustion engine, the waste heat of the internal combustion engine generally is not sufficient to heat the vehicle passenger compartment. In electric vehicles, no internal combustion engine is present so that heat for heating the air in the vehicle passenger compartment is provided exclusively by the electric heater. In this case, the hybrid vehicles or electric vehicles generally have a second coolant circuit with water as the coolant, which can be heated by the electric heater. The coolant in the second coolant circuit has an air heat exchanger, by means of which the heat from the coolant of the second coolant circuit is transmitted to the air in the vehicle passenger compartment.
The battery of the hybrid vehicle or electric vehicle must be heated or cooled in order to achieve an adequate operating temperature for the battery, for example in a temperature range between 0° C. and 40° C. When electrical energy is drawn from the battery, the battery gives off heat; in consequence, the battery must be cooled so that it does not heat to temperatures of above 30° C. or 40° C. At low outdoor temperatures, for example below 0° C., heating of the battery is necessary so that electrical energy can be drawn from the battery and also so that charging with electrical energy is possible. To this end, the hybrid or electric vehicle has a first coolant circuit with which the battery can be cooled, in particular with ambient air.
EP 1 264 715 A2, which corresponds to U.S. Pat. No. 6,705,101, which is incorporated herein by reference, and which discloses a vehicle cooling system for an electric or hybrid vehicle. The vehicle cooling system has a coolant circuit that is thermally coupled to a battery. Also built into the coolant circuit with the battery is an evaporator of a refrigeration circuit with a condenser, a compressor, and an expansion valve. The coolant circuit with the battery can be cooled by means of the evaporator so that in this way the battery can also be cooled by means of the refrigeration circuit. The refrigeration circuit also has an additional evaporator by means of which the air in a vehicle passenger compartment can be cooled.